The present invention relates generally to optical display panels, and particularly, to optical display panels comprising an element for directing image light through a display screen. More specifically, the present invention relates to thin optical display panels comprising an element for directing image light through a display screen, which element is capable of enhancing contrast of the image when viewing the display screen.
Optical display screens are found in many common applications such as television, computers, and industrial and scientific equipment. Common display screens form images using a cathode ray tube (CRT) which is relatively long and requires a large enclosure.
Thin display screens of various forms are continually being developed for replacing CRTs for minimizing the screen envelope and overall weight. A common thin panel uses a liquid crystal display (LCD) for spatially modulating light therethrough for creating two-dimensional video images.
Image quality is based on resolution, brightness, contrast, and viewing angle, for example, which characteristics vary in performance according to the particular display screen configuration.
For example, rear projection, large screen television (TV) displays fail to achieve levels of brightness, contrast, resolution, and wide viewing angle of common CRT displays, due in part to the use of lenticular screens.
Similarly, common LCD displays also fail to match performance of typical CRT displays.
Another type of thin panel display includes thin optical waveguides laminated together in a thin wedge shape through which image light is internally reflected between a narrow inlet face and a large outlet screen. U.S. Pat. No. 5,381,502 describes an exemplary optical panel based on this technology being developed for improving performance of thin panel displays.
All of the above-identified types of display screens have inherently limited contrast capabilities. Contrast in a display screen is based on the apparent blackness of the unlighted screen itself. Images are produced by varying the amount of light in individual picture elements, or pixels, for both black and white and color images, with image blackness being provided when no image light is generated.
The various screens described above cannot themselves be totally black since no image light could be projected therethrough. Accordingly, a typical CRT screen includes an aperture mask which itself is generally black, and has apertures through which the image light is projected. The image thus perceived from such a screen appears black in those regions not illuminated by image light.
LCD displays modulate plain light at corresponding pixels which are either opaque or translucent for creating a video image, and cannot be black. Contrast therefrom is therefore limited.
And, the optical waveguide displays require transparent waveguides for channeling the light image, and contrast may be created by providing black cladding between the waveguides for enhancing contrast as described in U.S. Pat. No. 5,625,736.
In view of these inherent contrast limitations in typical thin panel display screens, it is desired to provide a thin panel display having high contrast in a relatively simple configuration for minimizing thickness and costs of production.
An optical panel includes a serrated first side, an opposite second side, and a black material provided therewith for intermittently blocking light transmission. Image light may be transmitted through the panel at portions of the serrations that are not provided with the black material, with contrast provided by the black material.